<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        .parent{
            width: 500px;
            height: 500px;
            border: 1px solid #333;
            display: flex;
            flex-direction: column;
            /*
                flex-direction:column;
                控制垂直
                justify-content space-evenly|space-between|space-around;
                控制水平
                align-items
            */
            justify-content: space-evenly;
            align-items: center;
        }
        .parent>div{
            width: 100px;
            height: 100px;
            border: 1px solid #333;
        }
    </style>
</head>
<body>
    <dir class="parent">
        <div>

        </div>
        <div>

        </div>
    </dir>
</body>
</html>